The final launch of Atlantis marks the end of the U.S. space shuttle program. The program was approved by President Nixon in 1972 as NASA’s main undertaking after Apollo, and the first shuttle mock-up (shown above) was constructed at NASA’s Marshall Spaceflight Center in Alabama. Approximately the same dimensions and weight of the actual space shuttle, the mock-up was used to train workers; it is now on display at the U.S. Space and Rocket Center in Alabama.

The first space shuttle to fly was Columbia, shown here sitting on the launch pad before its maiden flight. (Enterprise was the first shuttle built, but it was initially not rated for spaceflight and only used for testing.) Columbia first launched on April 12, 1981, the 20th anniversary of the first human spaceflight, and was piloted by John Young, a Gemini and Apollo astronaut. Its first few missions were purely operational, for testing the spacecraft’s technical performance.

Canada made a key contribution to America’s shuttle program: a robotic arm that could maneuver payloads and serve as a platform for astronauts working outside the shuttle. The 15.2-meter arm was first launched on Columbia’s second mission, in November 1981, and it has since been used on over 50 shuttle missions. It can carry payloads up to 32.5 tons.

Astronaut Sally Ride was the first American woman in space. Her historic flight, in 1983, was aboard Challenger, the third orbiter in the fleet, as a mission specialist. Here, she is seen monitoring control panels from the pilot’s chair on the flight deck.

Weather is a significant factor for delaying shuttle launches. Here, Challenger moves through the fog on top of the “crawler” en route to the launch pad, which can be seen in the distance, 3.5 miles away. The weather did not affect the 12,000-pound orbiter’s trip to the launch pad, which took over six hours.

Astronaut Guion Bluford became the first African-American in space when he flew aboard Challenger in 1983. Here, he is restrained by a harness and wears a blood-pressure cuff on his left arm as he exercises on a treadmill.

A jet-propelled backpack called the Manned Maneuvering Unit (MMU) allowed astronauts to go “free-flying” in space. Here, astronaut Bruce McCandless is seen wearing the MMU in 1984. He traveled over 97 meters away from the shuttle, the furthest distance ever traveled by an untethered astronaut. The MMU is controlled by joysticks positioned at the end of the armrests, and nitrogen jet thrusters that can propel an astronaut in any direction.

On January 28, 1986, Challenger and her seven crew members were tragically lost due to an explosion that occurred seconds after the shuttle launched. Debris from the shuttle is seen here on the launch pad at Kennedy Space Center.

One of the key functions of the shuttle was carrying large satellites to low-Earth orbit. Here, the Galileo spacecraft is being prepared for launch onboard Atlantis, the fourth orbiter in the fleet, on October 12, 1989. Galileo was the first spacecraft to orbit the outer solar system; its mission was to survey Jupiter.

The Hubble Space Telescope, one of the largest space telescopes ever built, was carried into orbit by Discovery in 1990, and is the only telescope designed to be serviced in space by astronauts. A total of five servicing missions have been conducted, the final mission in 2009. Here, astronauts can be seen servicing the telescope in 1993, while it is connected to the shuttle’s payload bay.

Spacehab was a pressurized habitable module used for experiments that was carried inside the shuttle’s cargo bay. It was derived from the European Space Agency’s Spacelab, a science laboratory given to NASA in exchange for flight opportunities. Spacehab first flew in 1993, and is visible here in Endeavour’s cargo bay while astronauts work outside the shuttle.

In 1995, the Russian space agency and NASA started a new era of international cooperation when Atlantis docked with the Russian space station Mir for the first time.Atlantis and Mir became the largest combined spacecraft ever in orbit. The Shuttle-Mir program involved 11 shuttle missions and seven astronaut residencies on Mir; it helped pave the way for the International Space Station now in orbit.

A U.S. laboratory called Destiny was delivered to the International Space Station aboard a shuttle in 1998, the same year that on-orbit construction on the station started. Destiny is the primary research laboratory for U.S payloads. In this image, a space robot called Dextre sits on top of Destiny.

In 2003, the world witnessed another devastating shuttle accident when Columbia broke apart during reentry into Earth’s atmosphere, killing all seven crew members. This image shows debris from Columbia being brought into a hangar, where the Columbia Reconstruction Project Team attempted to reconstruct the bottom of the orbiter as part of the investigation into the accident.

The Columbia accident was caused by damage to a piece of reinforced carbon-carbon (RCC) on the shuttle’s left wing. Following the accident, and on advice from an investigation board, Discovery’s RCC panels were removed and inspected, and dozens of changes were made to the orbiter. The mission launched in 2005.

The construction of the International Space Station, a laboratory for experiments and international cooperation, was perhaps the greatest accomplishment of the shuttle program. The shuttle delivered its final element to the space station in March. In-orbit construction will continue through 2012. The station will remain in orbit through 2020.

Atlantis sits on the launch pad at Kennedy Space Center awaiting its final mission.